The Fourth International Conference on Advanced Robotics was held in Columbus, Ohio, U. S. A. on June 13th to 15th, 1989. The first two conferences in this series were held in Tokyo. The third was held in Versailles, France in October 1987. The International Conference on Advanced Robotics is affiliated with the International Federation of Robotics. This conference was sponsored by The Ohio State University. The American Society of Mechanical Engineers was a cooperating co-sponsor. The objective of the International Conference on Advanced Robotics is to provide an international exchange of information on the topic of advanced robotics. This was adopted as one of the themes for international research cooperation at a meeting of representatives of seven industrialized countries held in Williamsburg, U. S. A. in May 1983. The present conference is truly international in character with contributions from authors of twelve countries. (Bulgaria, Canada, France, Great Britain, India, Italy, Japan, Peoples Republic of China, Poland, Republic of China, Spain, United States of America.) The subject matter of the papers is equally diverse, covering most technical areas of robotics. The authors are distinguished. They are leaders in the field in their respective countries. The International Conference on Advanced Robotics has always particularly encouraged papers oriented to the design of robotic systems, or to research directed at advanced applications in service robotics, construction, nuclear power, agriculture, mining, underwater systems, and space systems.